Apologies if this has already been posted here, I looked around and didn't see anything on it.
The link at the bottom offers a selection of books including quite a few Theravada books. They will ship them free of charge (they do of course accept donations).
They have an online order form, if you fill it out and copy/paste it into an e-mail you should hear back quickly. I had an e-mail confirmation within three days and the books arrived about 2 1/2 months later -- they sent all five that I requested and six other Theravada selections.
Also, the list of available titles changes, you might want to bookmark it and check in with them periodically.